This invention relates to conveyor systems having power-driven conveyor sections and, more particularly, to apparatus for accumulating conveyed articles along a conveyor line as the upstream supply of articles exceeds the downstream demand.
One of the most common article accumulation systems used on conveyor lines is the bi-di (bidirectional) table. Typically, a bi-di table includes a bidirectional conveyor belt arranged to run perpendicular to a main conveyor belt running along a portion of the main conveyor line. As the upstream supply of articles exceeds the downstream demand, articles build up on the main conveyor belt. Backpressure from the backed-up mass of upstream articles pushes articles onto the bi-di table, which runs in a direction away from the main conveyor line to make room for more of the excess articles. As the downstream demand increases, the direction of the bi-di belt is reversed to push the articles accumulated on the bi-di table back onto the main conveyor belt to meet the downstream demand. Instead of a bidirectional conveyor belt, other accumulation tables use a pusher bar that retracts to allow overflow onto the table and that pushes accumulated articles back onto the main conveyor belt as downstream demand increases.
In conveyor lines of this kind, the main conveyor belt is usually a rubber, plastic, or metal conveyor belt or chain across which the articles slide as the backpressure builds up or as the bi-di table transfers articles onto the main conveyor belt. This works well for many articles, such as cans and bottles. But some articles, such as tires, made of rubber or rubber-like materials do not slide so easily across flat belt surfaces because of friction. For these high-friction articles, some sort of pushing mechanism is often required to slide the articles across the belts. But the pushing mechanisms do not decrease the belt-to-article friction; they merely overcome it at the expense of added complexity, power consumption, and cost.
Thus, there is a need for a simple accumulation system that is especially effective with high-friction articles, such as tires.
This need and others are satisfied by an accumulation system embodying features of the invention. The accumulation system is part of a conveyor line conveying a mass of articles in a conveying direction. A transfer conveyor forms a segment of the conveyor line. The transfer conveyor line extends from an upstream end to a downstream end in the conveying direction. It extends laterally from a first transfer side to an opposite second side. An accumulation table is positioned next to the conveyor line at the first transfer side of the transfer conveyor. The accumulation table receives articles from the transfer conveyor as the upstream supply of articles exceeds the downstream demand. As the downstream demand exceeds the upstream supply, the accumulation table delivers accumulated articles to the transfer conveyor. The transfer conveyor comprises a roller-top conveyor belt traveling in the conveying direction. Salient portions of the rollers extend from the belt to support conveyed articles. The rollers are arranged to rotate about axes generally in the conveying direction to direct articles toward and to receive articles from the accumulation table.
Thus, the rollers effectively reduce the friction between the conveyor and the conveyed articles they support in low-friction rolling, rather than high-friction sliding, contact.